Processes for preparing a solid polymer matrix containing a core material by pressure cycling of supercritical fluid

A process for preparing a solid polymer matrix containing a core material, said process comprising the steps of:

• (a) providing a solid polymer, a core material and a fluid that is capable of existing in the supercritical state;
• (b) in a mixing vessel, mixing the polymer, core material and fluid at
• a temperature at or above Tc and
• a pressure at or above Pc,
• such that the fluid is in the supercritical state, wherein Tc and Pc are the critical temperature and the critical pressure, respectively, for the fluid;
• (c) without recovering the solid polymer matrix,
• (i) converting the fluid in the vessel to a sub-critical state by reducing the pressure in said vessel to below Pc and/or reducing the temperature in said vessel to below Tc, and then
• (ii) returning the fluid in the vessel to the supercritical state by increasing the pressure and/or the temperature in the vessel;
• (d) optionally repeating step (c) one or more times;
• and
• (e) releasing the pressure in the vessel and recovering solid polymer matrix containing the core material,
• provided that the core material does not comprise any of gonadotropin releasing hormone (GnRH), a GnRH agonist and a GnRH antagonist.